1. Field of the Invention
The present invention relates to a flush toilet apparatus that discharges waste to a drain pipe by wash water.
2. Description of the Related Art
Examples of known systems for supplying wash water to a bowl portion of a flush toilet apparatus include a system of using high water pressure in a water pipe to supply water (direct-pressure type) and a system of supplying water from a tank arranged at a high place (tank type).
Since the direct-pressure-type flush toilet apparatus directly supplies water in the water pipe to the bowl portion, continuous washing is possible. However, if the apparatus is installed in an environment with a low water pressure in the water pipe, the flow rate of the wash water is reduced, and there is a problem that the washing performance is reduced.
Since the tank-type flush toilet apparatus uses potential energy of water stored in the tank to supply the water to the bowl portion, a large amount of wash water can be supplied without being affected by the water pressure in the water pipe. However, continuous washing is difficult because water needs to be poured into the tank after washing, and there is a problem that the flush toilet apparatus is not suitable for a situation in which the apparatus is frequently used.
Other than the apparatuses, a flush toilet apparatus with a system of supplying wash water to a bowl portion by a jet pump is proposed in recent years. For example, a flush toilet apparatus described in Japanese Patent Laid-Open No. 2004-156382 includes a tank storing water, and a jet pump unit is submerged and arranged inside of the tank. The jet pump unit includes a throat pipe. One end of the throat pipe is connected to a channel toward the bowl portion, and an opening is formed at the other end. When water is injected from an injection nozzle toward the inside of the throat pipe through the opening, a jet pump action is induced, and a large amount of water flows inside of the throat pipe toward the bowl portion. Not only the water injected from the injection nozzle, but also the water stored in the tank is drawn in and flows inside of the throat pipe. Therefore, a large amount of water is supplied to the bowl portion.
In this way, the flush toilet apparatus with the system of supplying wash water by the jet pump is configured to supply a large amount of water to the bowl portion by the jet pump action. This can suppress the reduction in the washing performance when the apparatus is installed in an environment with a low water pressure in the water pipe. The total amount of wash water supplied to the bowl portion is substantially equal to a sum of the amount of water stored in the tank and the amount of water injected from the nozzle. Therefore, the amount of water that needs to be stored in the tank is smaller than in the conventional tank type, and the tank can be downsized. Although water needs to be poured into the tank after the completion of washing of the bowl portion, the time required to pour water is shorter than in the tank type. Therefore, continuous washing is possible even if the flush toilet apparatus is frequently used.
To efficiently generate the jet pump action, it is desirable that the channel length of the throat pipe arranged in the tank is as long as possible. Therefore, when the dimension of the tank in the front-back direction is reduced to improve the design of the flush toilet apparatus, the throat pipe (long) is arranged so that the central axis of the throat pipe is substantially along the left-right direction of the tank when viewed from the top. The opening on the upstream end portion of the throat pipe is arranged at a position near one of left and right end portions inside of the tank.
However, according to the configuration, air in the tank may be sucked into the throat pipe when wash water is supplied to the bowl portion, although washing is not completed. This may reduce the efficiency of the jet pump action. Such a phenomenon may be caused by the fact that the entire water surface in the tank is not horizontal, because water at a position far from the opening of the throat cannot smoothly reach the opening of the throat pipe in a tank with a short dimension in the front-back direction. More specifically, the water level near the opening of the throat pipe drops earlier than the water level at other positions, and this may expose the opening of the throat pipe on the water surface at an early timing despite the fact that an amount of water necessary for washing is not supplied to the bowl portion. The difference between the water level near the opening of the throat pipe and the water level at the other positions is generated particularly when the water in the tank is reduced.
The present invention has been made in view of the problem, and an object of the present invention is to provide a flush toilet apparatus with a system of supplying wash water to a bowl portion by a jet pump, wherein high washing performance can be exerted without reducing the efficiency of a jet pump action, even if an opening on an upstream end portion of a throat pipe is arranged near one of left and right end portions in a tank.